The present invention relates generally to cloud computing services for surveillance that connect to “Internet of Things” devices to protect homes and businesses from fire and burglary. Such cloud computing services utilize a combination of wired or wireless devices to communicate to remote technicians with “cloud” computers which can be located anywhere. The present invention relates to electrical systems that typically include an infrastructure comprised of mechanical framework, electrical connectivity, and means for disconnecting, regulating, controlling, distributing, and modifying the electricity. Conductors as used herein are conduits. Connectivity as used herein is a general term that includes attachment means used for the purpose of conducting water, chemicals, Direct Current (DC), Alternating Current (AC), or combinations thereof. The connectivity components are sometimes called connectors, plugs, sockets, terminals, receptacles, or junction boxes, among other names.
Without limitation, the focus of the present application is connectivity of electrical systems producing sufficient voltage to cause human trauma and associated arc faults which can cause fires and death. For example, photovoltaic (PV) systems that produce DC electricity directly from the sun's rays. Residential and commercial PV systems are constructed with PV modules that contain a number of interconnected solar cells. The electrical conductors that carry DC output from the solar cells in a PV module are conventionally connected to metal lugs in a “junction box” located on the back of the PV module. Several PV modules are often linked with connectivity to aggregate the current or voltage in what is commonly called a “PV String”. The conductors of individual PV modules are joined by one or more electrical connectors that provide connectivity; usually in a series fashion.
The present application is directed to preventing electrical arc faults in connectors that carry over 80 volts. The fault can be caused, for example only, by a manufacturing defect; overload, ohmic heating due to corrosion, or thermal expansion and contraction at the joints by the thermal dynamics of current on the conductor. Arc-faults in connectivity can occur even when the operating voltages and currents are within normal bounds; such as, but not limited to, improper installation, unsafe design, or small air gaps caused by differences in expansion of the conduit and metal contacts in the connector or a manufacturing defect.
The present application relates to diagnosing characteristics of an unsafe condition in an electrical system connectivity component such as a connector with a badly corroded electrically conductive guide (also known as a ferrule) that, unattended, will become more resistive and will likely result in an electrical arc fault that generates white hot plasma and intense heat resulting in conflagration of nearby materials and structures.
The problem of arc faults in PV systems is so serious that the National Fire Protection Association modified the 2014 National Electric Code (NEC), cited as #1 in the above List of Non-Patent Documents, with requirement 690.11 to prevent death and injuries resulting from electrocution and fires of PV systems. The NEC is a publically-available, non-patent document that, because of relevance to the state of art of electrical systems, is included in its entirety herein.
A presentation about arc faults in PV system connectivity is publicly documented in a presentation by Jay Johnson of Sandia Laboratories, entitled “Arc-fault detection and mitigation in PV systems: Industry progress and future needs,” at the 28 Feb. 2012, Denver, Colo., NREL Module Reliability Workshop, cited as #3 in the above List of Non-Patent Documents. Ohmic heating can occur in connectivity junctions, in wiring, junction boxes, combiner boxes, inverter boxes, and protection within the electrical distribution system.
There is another Sandia Laboratory Technical Report authored by B. Yang, K. Armijo, E. Schindelholz, K. G. Blemel, K. D. Blemel, and J. Johnson, entitled, “Photovoltaic Balance of System Connector Arc Fault Prognostics through Optical Monitoring,” (SAND2015-0883) that focuses on arc faults in connectors that join the anodes and cathodes conductors of PV systems. At the present time, the report is release, designated Limited Release due to its proprietary nature, and included as #5 in the List of Non-Patent Documents above.
The present application differentiates from devices for protection from unsafe electrical events which include, but are by no means limited to, arc fault detectors, circuit breakers, ground fault interrupters, and arc fault circuit interrupters that operate by detecting electrical surges, light of plasma, radio, and other emissions of an electrical discharge but do nothing to pre-empt an arc. Such protection devices are commonly connected to a relay or other disconnecting device that trips to stop electrical current flow when an arc occurs.
There is a pressing need for an improved means described in detail in the present invention that acts autonomously to detect characteristics that, unattended, increase the risk of arc-faults happening and, additionally, that employs means for purposes of signaling, indicating, or annunciating an unsafe condition in need of attention to homeowners, facility managers, or cloud computing services.